Recovery of alcohol from a ternary solution



Dec. 19, 1950 E. A. GEE ET AL RECOVERY OF ALCOHOL FROM A TERNARYSOLUTION 2 Sheets-Sheet 1 Filed Dec.

@RQQ

ill

NY Q

fow/N 14. GEE Jal/N VANDEN B 0 55cm;

INVENTOR ATTORNEY Dec. 19, 1950 E. A. GEE ErAL RECOVERY OF ALCOHOL FROMA TERNARY SOLUTION Filed Dec. 14, 1945 2 Sheets-Sheet 2 ts 31w INVENTORS ATTO R N EY f stantial amounts of ethanol.

advantages will be apparent or will'appear' here- Patented Dec. 19, 1950UNITED STATES PATENT OFFICE RECOVERY. OF ALCOHOL FROM A TERNARY SOLUTION1 Edwin A. Gee, Washington, D. 0., and John Vanden Bossche, Hyattsvilie,Md., assignors to the United States of'America as represented by theSecretary of the Interior Application December 14, 1945, Serial N 0.635,116 11 Claims; (Cl. 260-643) (Granted underthe act of March 3, 1883,as amended April 30, 1928; 370 O. G. 757) The invention described hereinmay be manufactured and used by or for the Government of the UnitedStates for governmental purposes without the payment to us of anyroyalty thereon in accordance with the provisions of the act of April30, 1928 (ch. 460,,45 5tat. L. 467).

.This invention relates to the'recovery of water soluble alcohols fromadmixture with aqueous solutions of inorganic salts, and moreparticularly relates to the recovery of ethanol from I concentratedaqueous alum solutions. Still more particularly this invention relatesto the recovery of ethanol from wet filter cakes of aluminum sulfatewhich have been produced by precipitation with ethanol from aqueousmother liquors.

In copending application Serial Number 617,- 888, filed September 21,1945, in the names of Edwin A. Gee et al., there has been disclosed away to produce practically iron-free aluminum sulfate by precipitationwith ethanol. This procedure produces a wet cake of aluminum sulfatecrystals which contain large proportions of Water of hydration, and avery considerable amount of alcohol. The alcohol can be removed andrecovered by vacuum distillation, but such a procedure is extremelytedious and so expensive as to render it prohibitive in commercialoperation. It has now been found that alcohols such as ethanol can berecovered from wet salts such as aluminum sulfate in a simple andexpeditious fashion as more fully to be explained hereinafter.

Accordingly, this invention has for an object the recovery of watersoluble alcohols from aqueous solutions of inorganic salts.v Anotherobject of this invention is the recovery of ethanol from wet filtercakes of alums containing sub- Other objects and inafter as the ensuingdescription proceeds.

, Theseobjects are accomplished'in accordance with this inventionwhereina water soluble alcohol such as ethanol is recovered from admixture withwater and alums such as aluminum sulfate, by adjusting. the compositionofjsuch a mixture to proportions permitting formation of two liquidphases, then bringing the mixture to a temperature at which formation oftwo liquid phases takes place, and separating the alcohol-rich phasefrom the alcohol-poor phase. It has been discovered that within certainranges of compositions, the liquid systems aluminum sulfate-ethylalcohol-water will separate and stratify into two liquid phasescontaining different proportions of alcohol in each of the liquidphases. It has also been discovered that the proportion of alcohol ineach liquid phase is very largely influenced by the temperature at whichthe solution or solutions is or are maintained; that is, at elevatedtemperatures approaching the boiling point of the particular alcoholemployed, the two liquid phases have a very markedly different contentof alcoholfor example at degrees, the upper layer corresponding to theless dense phase, contains of the order of ten times as much alcohol asthe lower layer. This observation thus permits the separation andrecovery of ethanol and other alcohols from concentrated solutions ofaluminum sulfate, in a simple and expeditious manner by heating thesolution to a temperature approaching the boiling point, stratifying themixture into two phases, and separating the alcohol-rich phase from thealcohol-lean phase.

In order to secure the necessary two liquid phases, it has been observedthat the composition or proportions of alcohol to water to alum or otherinorganic salt must be adjusted within certain limits. At relatively lowtemperatures of the order of 30 degrees C., only a very narrow range ofcompositions will yield the necessary 2- 'phase system. However, it hasbeen observed and will be more fully explained hereinafter, that atelevated temperatures below the boiling point of the alcohol, preferablyat temperatures of about 80 degrees C., a relatively broad range ofcompositions will yield a Z-phase system, that is will stratify into twoseparate and distinct liquid layers. Thus, the composition necessary toyield two liquid phases is dependent upon the temperature at which theliquid system is mainl tained.

Fortunately, in the recovery of alcohol such as ethanol from wet filtercakes containing also alum and water, simple heating of the filte cakeresults in a melting or dissolution of the alum in its water ofhydration whereby there is formed a concentrated aqueous solution or"aluminum sulfate or other alum in its water of hydration and of course,in the alcohol to be recovered. To produce a composition within thenecessary limits yielding a 2-phase liquid system at temperaturesbetween 30 degrees C. and the boiling point of the alcohol from such wetfilter cakes, it is only necessary to add a sufficient quantity of waterto the hot solution to bring the composition within the desired range.Preferably, for reasons of economy in alum recovery and in order toyield a concentrated alcohol, it is desirable to incorporate with thealum melt only a minimum of water. The exact quantity of water necessaryto yield a Z-phase system for any particular aluminumsulfate-alcohol-water mixture can readily be determined from aninspection or the accompanying drawings and ensuing tabulated phasedata.

In the drawings:

Fig. 1 is a phase diagram of the system aluminum sulfate-ethanol-waterat 30 degrees C.

Fig. 2 is a phase diagram of the system aluminum sulfate-ethanol-waterat 80 degrees C.

In Fig. 1, the solubility of aluminum sulfate separated by the 2-1iquidcurve EPF. The points E and F are the isothermally invariant conjugatesolutions in equilibrium with the solid. The curve QR representssolutions in equilibrium with the decahydrate and RG representssolutions saturated with the anhydrous salt. Q and R are theisothermally invariant solutions saturated in each case with two solids,the hexadecahydrate and the decahydrate for the former point, and thedecahydrate and anhydrous salt for the latter point.

In Fig. 2, the solubility of aluminum sulfate decahydrate in aqueousalcohol solvents is represented by the curves DE and FR, which areseparated by the 2-liquid curve EPF corresponding to Fig. 1. The curveRG represents solutions in equilibrium with the anhydrous salt, and thepoint B is the isothermally invariant solution saturated both withdecahydrate and anhydrous salt.

The following Tables I and II show in tabulated form the equilibriumdata for the system aluminum sulfate-ethyl alcohol-water at 30 degreesC. and at 80 degrees C. In the table, the headings Total Composition andComposition of Solution refer respectively to the compositions of theinitial overor under-saturated mixture and to the final solution inequilibrium with solid phase. The heading A. S. refers to anhydrous saltwhich in the caseof Tables I and II, is anhydrous aluminum sulfate. Thetables were hexadecahydrate in alcohol-Water solvents is constructed byordinary physical chemistry represented by the curves DE and FQ, whichare methods Table I [Equilibrium data for 30 isotherm, 30]

ggfisg Composition 01 Solution Solid Phase Percent Percent A. S IttOHEtOH Density 2. 8 (G) 97. 1 0. 1 99. 8 0. 781 A12(SO-1)3. 3. 3 93. 0 196. 0 0. 790 D0. 3. 1 R) 91. 8 1 95. 1 791 1112(SO413 andA12(SOU3.10H20. 1.0 91.2 .0 92.6 .800 A12(SO-l)s.10H2O. 1.8 88.6 .0 90.8.804 Do. 2. 7 80. 5 0 83. 5 824 D0. 1.0 76.0 .0 77.5 .841 D0. 3. 5 66. 80 70. 1 861 D0. 2. 4 66. 6 0 69. 1 863 D0. 1.6 66.0 .0 67.8 .867 Do. 5.2 (Q) 60. 8 .0 66.4 .870 Alz(SO4)a.l0HzO and A12(SO4)3. 161120. 2.0 62.0.0 64.0 .878 A12(SO-i)3.16H20. 1.7 60.4 .1 62.4 .881 D0. 3. 2 56. 5 259. 4 882 D0. 4. 1 54. 5 2 58. 8 892 D0. 4. 8 52. 3 3 56. 8 898 D0. 3.350.8 .4 53.5 .908 D0. 2.9 49.1 .7 51.8 .913 D0. 5.2 45.3 1.0 49.9 .919D0. 6.0 41.8 1.4 46.0 .924 D0. 6. 1 38. 2 2. 8 40. 9 935 D0.

Double layer 1 I p Bottom Percent Percent Percent Percent A. EtOH DBDSW11.8. EtOH Deng 13.2 (E & 1*) 24.7 3.8 38.1 (P) 0.947 19.5 15.5 (E)1.102 10. 2 27. 7 6. 9 33. 0 0. 957 15. 3 20. 0 0. 990

Solid phase 11. 4 26. 1 11. 4 26. 1 1. 038 1112(8 003. 161110. 24. 2 11.4 20. 3 13. 0 1. 186 D0. 24. 2 7. 3 22. 5 8. l 1. 223 D0. 27. 2 2. 0 26.6 2. 0 1. 293 D0. 28. 7 (D) 0. 0 27. 7 0. 0 1. 302 D0.

1 Aluminum sulfate hexadecehydrate is the solid phase throughout.

Table II [Equilibrium data for 80 isotherm, 80]

il g e gfi Composition of Solution Solid Phase A. s EtOH i g gg Density3 (G) 96. 8 0.9 98. 9 0.745 A12(SO4)2. 2 0 90. 9. 7 92. 0 759 D0. 2 484.3 .3 86. 3 776 D0. 2. 81. 0 1 83. 0 783 D0. 3, 1 (Q) 77. 5 0 80.0 790A12 SO4 2 and A12(SO4)2.10H2O. 2.1 73. 3 .1 74. 9 .812

Double layer 1 Top Bottom Per Cent Per Cent Per Cent Per Cent A. s. EtOHDeng? A. s. EtOH 30, 1 (E & F) 19. 1 2.0 63. 5 (F) 0.840 38.0 6. 9(E) 1. 345 22. 8 29. 2 1. 9 62. 1 8-18 36. 4 7. 2 1. 320 15. 3 38. 9 2.0 60. 8 854 32. 8 9. 1 1. 285 27. 7 17. 7 2. 0 60. 5 856 32. 9 9.0 1.280 21. 1 26. 9 3. 0 56. 5 860 32. 2 9. 3 1. 230 14. O 36. 4 3. 4 52. 4871 29. 4 11. 5 1. 210 25. 7 16. 4 4. 5 50. O 903 28. 5 11. 5 1. 200 19.5 25. 0 5.5 47. 3 912 27. 2 12. 8 1. 152 13.0 33. 7 6. 6 44. 0 918 25. 0l4. 0 1. 143 18.2 23. 2 I 8. 4 38. 8 964 23. 2 15. 5 l. 132

Solid Phase 24. 0 15. 3 24. 0 15. 3 1. 131 A1r(SO.l)s.1OH2O. 1 7. 5 22.O 17. 5 22. O 1. 042 D0. -12. 3 31-. 0 12. 3 31. 0 0 990 D0. 40. 5 3. 539. 4 5 Do. 43. 5 (D) 0. 0 42. 2 0.0 D0.

1 Aluminum sulfate decahydrate is the solid phase throughout.

An examination of the phase diagram in Fig. l and the tabulated data inTable I shows that the area enclosed by the closed traverse on Fig. 1passing through the points EPFE is the locus of all compositions havingthe property of separating into two liquid phases at this particulartemperature. In Fig. 2 and referring to the tabulated data of Table II,it will be seen that the area of the phase diagram bounded by the closedtraverse EPFE 'inFig. 2 is also the locus of all compositions which willyield a 2-phase system. However,at 80 degrees C., the area enclosed bythe points EPFE is very much larger than it is at degrees C. Thisrelation appears to obtain at increasingly elevated temperatures up tothe point at which substantial amounts of alcohol are lost by boilingout of the solution. Therefore, it is preferred to employ an elevatedtemperature which is, however, below the boiling point of the solution.Reference to the data under the heading Double Layer in both Tables Iand II clearly shows the striking difference in alcohol contents betweenthe upper and lower layers at elevated temperatures even though there isa substantial difference in the alcohol content at temperatures as lowas '30 degrees C.

In the practical application of this invention, ordinar aluminum sulfatewet filter cake produced by crystallization from aqueous alcoholsolutions or by any other means yielding an alcoholcontaining wet filtercake, is heated to an elevated temperature below the boiling point ofethyl alcohol or other lower water soluble alcohol, and thereupon thefilter cake melts, dissolves in its own water of crystallization as wellas in retained mother liquor, and ordinarily yields a 3-phase system.The melting operation can be carried out in any suitable vessel,provided with heating and cooling means and with means for decanting orotherwise separating an upper stratified liquid layer from a lowerliquid layer. Thereupon, suffi cient water, preferably heated also toapproximately degrees C., is slowly added with agitation until a trialstratification test discloses the formation of two separate liquidphases. The lower liquid phase is then drawn off, as by a suitablepetcocl; in the vessel, and is thereby separated from the upper oralcohol-rich liquid phase. If desired, the lower liquid phase can becollected to yield, on cooling, a purified alum cake containing onlyvery small amounts of ethyl alcohol or other alcohol, or optionally, thelower liquid phase can be subjected to ordinary distillation to recoverthe last traces of its contained alcohol. The upper liquid layer, whichis very rich in alcohol, can be suitably enriched with concentratedalcohol and directly used for the further precipitation and purificationof alum. Optionally, a proportion of the upper layer can be withdrawn,subjected to ordinary distillation and rectification to recoverconcentrated alcohol therefrom, and the balance of the upper layer canthen be enriched directly with this recovered alcohol for reuse inpurification of further quantitles of alum. Another optional procedureis to subject the whole of the upper or alcohol-rich layer to ordinarydistillation and rectification whereby substantially the whole of thealcohol is recovered therefrom by very simple and inexpensive means.

From the foregoing it will be seen that a simple and inexpensive way hasbeen provided to recover ethanol or other suitable lower aliphatic watersoluble alcohol from concentrated solutions of mineral salts such as thealums and particularly aluminum sulfate.

Example of decantation drying 100 pounds of washed alum cake wet withalcoholic wash liquor is discharged from a suitable filter into ajacketed tank equipped with heating coils and decantation apparatus. Thecake had the following composition:

Wash liquor retention 50% by wt. liquor Wash liquor strength 68% C2H5OHAlum hydrate 16% H2O Alum (dry), 27 lbs 27% Alcohol, 34 lbs 34% Water,39 lbs M. 39%

Twenty pounds of water was added to yield the following composition:

Per cent Alum, 27 lbs 22.5 Alcohol, 34 lbs 28.3 Water, 59 lbs 49.2Composition of two phase system at 80 C.

Per cent Top layer (total), 48 lbs 40.0 Alum, 0.9 lb 1.9 Alcohol, 29.7 l61.9 Water, 17.4 lbs 36.2 Bottom layer (total), '72 lbs 60.0 Alum, 26.5lbs 36.8 Alcohol, 4.9 lbs 6.9 Water, 40.6 lbs 56.3

The top layer is then decanted and may be recycled while the residualalcohol in the bottom layer is removed by steam sparging ordistillation. The desired concentration of the alum is then obtained bycontinuation of the above.

While the invention has been described with particular reference to therecovery of ethanol from aluminum sulfate, for example filter cakescontaining also mother liquors and ethanol, it is also applicable to thetreatment of such alums as potash alum, chrome alum, and similarinorganic salts. Likewise, other suitable alcohols can be used such asfor example methanol, normal and isopropanol, and similar lower watersoluble alcohols.

Various changes can be made in the invention as disclosed withoutdeparting from the spirit and scope thereof, since many apparentlydiffering embodiments of this invention will occur to one skilled in theart.

What is claimed is:

1. In a process for the recovery of a watersoluble alcohol fromadmixture with aluminum sulfate and water, the steps which compriseadjusting the composition of such a mixture to proportions permittingformation of a two-phase liquid-liquid system, then bringing the mixtureto a temperature at which formation of said twophase system takes place,and separating the alcohol-rich phase from the alcohol-poor phase.

2. In a process for the recovery of ethanol from admixture with aqueousaluminum sulfate solution, the steps which comprise adjusting thecomposition of such a mixture to lie within the area bounded by LPFE onthe accompanying phase diagram (Figure l) heating the mixture to causeseparation into two liquid phases, and removing and recovering thealcohol-rich phase from the alcohol-poor phase.

3. A process for the removal of ethanol from an aqueous solution formedby melting alcoholcrystallized, hydrated aluminum sulfate, whichcomprises incorporating sufficient water into such a solution to permitformation of a two-phase liquid-liquid system upon heating, and thenheating the solution to a temperature not higher than the boiling pointof alcohol whereby said two liquid phases are formed, and separating thealcohol-rich phase from the alcohol-poor phase.

4. A process for the recovery of ethyl alcohol from an aqueous alcoholicsolution of aluminum sulfate, which comprises adjusting the watercontent of the mixture to permit formation of a twophase liquid-liquidsystem upon heating, and. heating the mixture to a temperature of aboutdegrees centigrade whereby Stratification into alcohol-rich andalcohol-poor layers results, and separating and recovering thealcohol-rich layer.

5. In a process for the recovery of a watersoluble alcohol fromadmixture with aluminum sulfate and water, the steps which compriseadjusting the total composition of such a mixture to lie within the areabounded by the locus of the conjugate solutions of the triaxial systemon a three phase diagram for a predetermined temperature not greaterthan the boiling point of the alcohol, heating said adjusted mixture tosaid predetermined temperature whereby the conjugate solutions stratifyin an alcohol-rich phase floating on an alcohol-poor phase, andthereafter separating the stratified phases.

6. In a process for the recovery of ethanol from admixture with aluminumsulfate and water, the steps which comprise adjusting the totalcomposition of such a mixture to lie within the area bounded by thelocus of the conjugate solutions of the triaxial system on a three phasediagram for a predetermined temperature not greater than the boilingpoint of ethanol, heating said adjusted mixture to said predeterminedtemperature whereby the conjugate solutions are formed and stratify asan alcohol-rich phase floating on an alcohol-poor phase, and thereafterseparating the Stratified phases.

"1. In a process for the recovery of ethanol from admixture withaluminum sulfate and water, the steps which comprise adjusting the totalcomposition of such a mixture to lie within the area bounded by thelocus of the conjugate solutions of the triaxial system on a three phasediagram for a predetermined temperature between about 30 and 86 degreesCentigrade, heating said adjusted mixture to said predeterminedtemperature, whereby the conjugate solutions of said adjusted totalcomposition are formed and stratify, as an alcohol-rich phase floatingon an alcohol-poor phase, and thereafter separating the alcohol-richphase and the alcohol-poor phase.

8. A process for the recovery of ethyl alcohol from admixture of ethylalcohol, water, and aluminum sulfate which comprises adjusting theconcentration of at least one of the admixture components so that thetotal composition of the admixture will be capable of resolving into theconjugate solutions of said adjusted total composition at apredetermined temperature not greater than the boiling point of saidalcohol, heating said adjusted composition to said predeterminedtemperature to effect the formation of the conjugate solution, one ofsaid conjugate solutions being an alcohol-rich phase and the otherconjugate solution being an alcohol-poor phase, and then suitablyseparating the alcoholrich phase from the alcohol-poor phase.

9. in a process for the production of aluminum sulfate, involving theprecipitation of alum from an aqueous solution by the addition theretoof ethyl alcohol and separating the crystallized aluminum sulfate fromthe mother liquor, the im- 9 proved method for the recovery of the ethylalcohol values entrapped in the wet crystalline alum, which comprisesadjusting the total composition of the aluminum sulfate-water-ethylalcohol mixture so it will contain about 1.5 to 38 percent aluminumsulfate, 6 to 63 percent ethyl alcohol, and 34 to 61 percent water,heating said adjusted composition to about 80 degrees centigrade, andseparating the resulting stratified liquid phases whereby an enrichedalcohol solution suitable for recycling is recovered as the lighterliquid phase.

10. In a process for the production of aluminum sulfate, involving theprecipitation of aluminum sulfate from an aqueous solution by theaddition thereto of ethyl alcohol and separating the crystallizedaluminum sulfate from the mother liquor, the improved method for therecovery of the ethyl alcohol values entrapped in the Wet crystallinealum, which comprises adjusting the total composition of the aluminumsulfate-water-ethyl alcohol mixture so it will contain about 22.5percent aluminum sulfate, 28.3 percent ethyl alcohol, and 49.2 percentwater, heating said adjusted composition to about 80 degrees centigrade,and separating the resulting stratified liquid phases whereby anenriched alcohol solution suitable for recycling is recovered as thelighter liquid phase.

11. In a process for the recovery of ethanol from admixture of aqueousaluminum sulfate solution, the steps which comprise adjusting thecomposition of such a mixture to lie within the area bounded by EPFE onthe accompanying diagram (Figure 2), heating the mixture to causeseparation into two liquid phases, and removing and recovering thealcohol-rich phase from the alcohol-poor phase.

EDWIN A. GEE.

JOHN VANDEN BOSSCHE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,985,205 Derr Dec. 18, 19342,013,804 Klein Sept. 10, 1935 2,123,554 Klosky July 12, 1938 2,137,605Derr Nov. 22, 1938 2,398,338 Walker Apr. 9, 1946 2,421,375 Elliott June3, 1947 OTHER REFERENCES

1. IN A PROCESS FOR THE RECOVERY OF A WATERSOLUBLE ALCOHOL FROMADMIXTURE WITH ALUMINUM SULFATE AND WATER, THE STEPS WHICH COMPRISEADJUSTING THE COMPOSITION OF SUCH A MIXTURE TO PROPORTIONS PERMITTINGFORMATION OF A TWO-PHASE LIQUID-LIQUID SYSTEM, THEN BRINGING THE MIXTURETO A TEMPERATURE AT WHICH FORMATION OF SAID TWOPHASE SYSTEM TAKES PLACE,AND SEPARATING THE ALCOHOL-RICH PHASE FROM THE ALCOHOL-POOR PHASE.